1. Field of the Invention
The present invention relates to a centrifugal fan, and particularly, the present invention relates to a centrifugal fan such as a compact sirocco fan and a turbo-fan or the like.
2. Description of the Related Art
In a centrifugal fan for use in electronics devices, the size of the centrifugal fan in a direction perpendicular to a rotation axis (namely, a radial direction) may be restricted or the size of the centrifugal fan in a rotation axial direction (namely, an axial direction) may be restricted. In this case, it is necessary to reduce the size of an air channel of a casing having a motor and an impeller therein or, in addition to this, to reduce the diameter of the impeller. However, in the centrifugal fan having such configuration, there is a problem that the performance is lowered and the noise is increased.
Therefore, among such centrifugal fans, there is a configuration such that an inner cross section of the air channel is enlarged in the axial direction from the middle of the air channel through an air outlet.
However, in these arts, there is no reference to problems such as restriction of the size of the centrifugal fan in a direction perpendicular to a rotation axis and lowering of the performance due to miniaturization of the air channel and the impeller caused by the restriction.